Process for sealing a top-opening carton

ABSTRACT

A process for closing a top-opening carton by providing flaps corresponding in shape to a movable segment of the wall panel to which it is to be attached. Each such flap is tucked inside the corresponding movable segment of the wall panel and caused to adhere to the inside of the movable wall segment by the use of hot or cold adhesive or by heat sealing (softening and mating of thermoplastic coatings on the surface of the paperboard). The resiliency of paperboard proximate to score lines and its tendency, when bent along a score line, to return to its original flap plane, provides sufficient back pressure in the flap to force it into intimate contact with the inner face of the movable segment of the wall panel resulting in effective bonding of the flap to the segment along its entire length.

United States Patent Stuberg [451 May 16, 1972 PROCESS FOR SEALING A TOP- OPENING CARTON Robert 0. Stuberg, I01 Bella Vista Drive, Hillsborough, Calif. 94010 [22] Filed: May 13,1970

[2|] AppLNo: 36,735

[72] Inventor:

3,507,440 4/l 970 Stuberg ..229/33 Primary xaminer-Robert L. Spruill Attorney-Townsend and Townsend ABSTRACT A process for closing a top-opening carton by providing flaps corresponding in shape to a movable segment of the wall panel to which it is to be attached. Each such flap is tucked inside the corresponding movable segment of the wall panel and caused to adhere to the inside of the movable wall segment by the use of hot or cold adhesive or by heat sealing (softening and mating of thermoplastic coatings on the surface of the paperboard). The resiliency of paperboard proximate to score lines and its tendency, when bent along a score line, to return to its original flap plane, provides sufficient back pressure in the flap to force it into intimate contact with the inner face of the movable segment of the wall panel resulting in effective bonding of the flap to the segment along its entire length.

9 Claims, 4 Drawing Figures PATENTEDHY 15 W2 FIG ..3

INVENTOR. ROBERT O. STUBERG TQM IE AT fORNEYS PROCESS FOR SEALING A TOP-OPENING CARTON This invention is directed to a process for closing and effectively gluing or sealing a top-opening carton. While applicable to closing of uncoated, non-barrier paperboard cartons, it is particularly valuable when used in conjunction with canons having coatings applied to them for the purpose of inhibiting the transmission of moisture vapor, gases, flavors, odors, etc., either into, or out of, the carton.

Present commercially available top-opening (top-closing) cartons utilize a lid hingedly secured along one edge thereof to one side wall panel of a rectangularly shaped body. Flaps extend outwardly from the other three edges of the lid to provide an overlap with the respective wall panels of the body. in operation the body is filled with the particular material being packaged and the lid positioned to cover the body opening. Then the overlapping flaps are adhered (or locked by means of male and female locking cuts and tabs) to respective wall panels to retain the lid member as a closure for the opening in the body. The method for adhering the flaps to the walls of the body conventionally involves, for example, applying glue and pressure for overlapping attachment or by interlocking of the flaps and respective wall panels. Alternately, where the carton blank is formed with a thermoplastic surface coating, appropriate portions of the coating can be first sofiened and thereafter the flaps are retained in contiguous association with respective of the wall panels of the body while the tacky thermoplastic coating is allowed to cool and solidify. The adherence is normally accomplished along the lower portion of the respective wall panel where the bottom panel provides the necessary back-up pressure. in this manner, the flaps are secured to the body, thereby providing an integral enclosure, until the carton contents are to be utilized.

Although this type of canon closing is quite satisfactory when no barrier is required or when it is employed in conjunction with the application of a tightly sealed overwrap of a material designed to inhibit the transmission of moisture vapor, gas, flavor, odors, etc, it is wasteful of materials as it uses more paperboard than is required to encompass the product. When the carton is formed of coated paperboard designed to reduce the transmission of vapor, gas, flavor, etc., the conventional method of closing top-opening cartons does not provide continuous, effective adherence and leaves labyrinthian passages and/or openings in the carton through which vapor, gases, odors, etc. can pass. The reason for this is that conventional sealing methods, wherein the overlapping flaps are adhered to the wall panels along the edge coextensive with the bottom panel, allow for moisture/vapor leak along the opposite unsealed edges of each flap.

This undesirable feature is not minimized by reducing the width of the overflap because less resistance is provided by the central portion of the corresponding panel. Although the side panel may be rigid along the score lines forming its side edges and lower edge (where back pressure is provided by the adjoining perpendicular panel), the internal area of each wall panel is quite flexible. Furthermore, the upper portion thereof also provides insufficient resistance of "back pressure" in opposition to the force applied for accomplishing physical con tact between the overlapping flap and the front wall panel. As a result, the desired adherence is not obtained.

When the overflap is reduced in width, the difficulty of obtaining sufficient back pressure is compounded, and the shorter the overflap the more difficult it becomes to achieve uniform contact and adherence. in other words, with present carton structures, sufiicient pressure cannot be applied along the overlap front flap and against the whole front wall panel to create uniform contact and adherence. Thus, the continuity of seal necessary to form an adequate vapor, gas, odor, etc. barrier along the front of the canon cannot be provided.

It is the principal object of this invention to provide a process for carton closure that produces a good continuous bond which eliminates labyrinthian passages or openings.

it is another object of this invention to provide a method for carton closure wherein such closure is more effective with substantially less paperboard.

It is a further object of this invention to eliminate the need for a barrier overwrap or an inner heat-sealed plastic bag (innerwrap) in consumer packages.

it is another object of this invention to provide a method for effectively sealing a top-opening carton at speeds currently employed in assembling lock or glue style closures.

it is a feature and advantage of this invention to utilize flaps that tuck within the upper portion of any or all wall panels of a top-opening carton so that when pressure is applied against the upper portion of the wall panel, the pressure will be resisted by both the natural resiliency of the flap to spring back about the score line between the flap and the lid, and the edge rigidity of the top panel.

These objects, features and advantages will be better understood and others will become apparent when reference is made to the following detailed disclosure especially in view of the attached drawing wherein:

FIG. 1 is a plan view of a carton blank showing one embodiment incorporating the features of this invention; and

FIGS. 2, 3 and 4 are partially cutaway perspective views illustrating the sequential steps involved in obtaining the finished carton of this invention from the embodiment of FIG. 1.

Referring more particularly to the drawing, wherein similar characters of reference represent corresponding parts in each of the several views, in FlG. 1 there is shown a carton blank A that has been formed from a flat sheet of flexible material in a conventional manner such as with rotary blank-forming (diecut forming) paperboard manufacturing equipment.

For purposes of illustration only, the remainder of the specification will be directed to the method of sealing the front flap. However, it will be readily apparent to one skilled in this art that the method is equally applicable to the side flaps.

Blank A includes a number of longitudinal score lines 10 and a number of transverse score lines 12 disposed to form bottom panel 14, top panel 16 and side panels 18, 20, 22 and 24. Flaps 26, 28 and 30 are hingedly attached to top panel 16 along respective of score lines 10 and I2. Side panels 18 and 22 are also provided with flaps 32, 32', 32" and 32" extending from respective of their edges for attachment to respective portions of side panels 20 and 24, such as by gluing, to form a rectangular body from blank A. It will be apparent to one skilled in the art that gluing is merely one of a number of methods of interconnecting the various side walls to provide a rectangular body for the carton. The body of the carton may also be formed by interlocking tongues and slits as well as by heat sealing the flaps to the side panels.

Turning more specifically to side panel 22, it includes a score line 36 intermediate the height of panel 22 and extending for a substantial part of the length thereof. Slits 38 and 38' extend from respective ends of score line 36 out to the outer edge of panel 22. Also contemplated within the scope of this invention are slits 38 and 38' that extend perpendicular to score line 36, thereby providing a rectangular upper segment 40. In either case, slits 38 and 38', score line 36, and the outer elongated edge of side panel 22 define the upper segment (portion) 40. Extension 28 is formed with an outer edge 42 and side edges 44 and 44' to provide a flap corresponding in configuration to upper segment 40 of panel 22. in this manner, after extension 28 is inserted within the body of the carton formed by blank A, upper segment 40 can be bent away for inserting glue (hot or cold adhesive) or for heating a thermoplastic coating on the outer surface of extension 28 and the inner surface of segment 40. Although it is preferred for both flap 28 and upper segment 40 to be of trapezoidal configuration, a corresponding rectangular configuration also enables segment 40 to be moved out of the plane of side panel 22 to allow for insertion of flap 28 within the body of the carton.

Referring now to FIGS. 2-4 depicting the assemblage of carton 8, body portion including bottom panel 14 and side wall panels 18, 20, 22 and 24 are assembled in a conventional manner. Thereafter, flaps 26 and 30 are secured to respective of side walls 24 and 20.

Referring to FIG. 3, flap 28 is inserted entirely within the plane of panel 22. The inside of side wall panel 22 is then used as a vehicle for applying heat or adhesive to the overlapping portions of portion 40 and flap 28. Thus, upper portion 40 is moved out of the plane of wall panel 22 to allow for the insertion of a heated die or the like between portion 40 and flap 28. Conversely, upper portion 40 could be first moved out of the plane of wall panel 22 to provide a path of ingress for flap 28 as shown most clearly in FIG. 2. Insertion of the heated die between the inner surface of upper segment 40 and the outer surface of flap 28 is one method for elevating the temperature of the thermoplastic coating so that it will become tacky. Thereafter, pressure can be applied against the outside surface of upper segment 40 so that the inside thereof is forced into intimate contact with the outer surface of flap 28.

Flap 28, because of the resiliency of the flexible material comprising blank A, tends to spring outwardly around score line 12 towards its original flat position. in this manner, flap 28 will push back against the force being applied to upper portion 40 and provide the continuity of contact required to obtain an adequate seal. it will be apparent to one skilled in this art that as the width of flap 28 increases, the resiliency of the flap will diminish. Thus, it is preferable to form flap 28 with as small a width as possible. In this manner, optimum advantage is also obtained from back-up support provided by top panel 16. In this regard, it has been found most advantageous to utilize a flap 28 having a width no greater than half the height of panel 22 and preferably of from about one-half inch to five-eighths inches wide.

In a preferred embodiment, and as shown most clearly in FIG. 3, it is desirable that flap 28 have a slightly larger crosssectional area than upper portion 40. In this manner, when segment 40 is sealed against flap 28, the surface of flap 28 will overlap slits 38 and 38 and ensure a more effective moisturevapor barrier.

The thermoplastic surface coating employed in this invention can be any of those presently commercially available to the packaging industry including polymers of polyethylene and the like. Such coating materials are suitable for direct oncarton printing and are especially advantageous in this invention where the need for a printed overwrap is diminished. Alternatively, uncoated cartons can be similarly sealed through application of conventional cold adhesives.

Although the foregoing invention has been described in some detail by way ofillustration for purposes of clarity of understanding with respect to the front flap, it will be apparent to one skilled in this art that the side flaps can be similarly sealed and certain changes and modifications may be practiced within the spirit ofthis invention.

I claim:

l. A method of closing a top-opening canon having a lid including at least one extension for contiguous association with a wall panel having an upper segment movable from the plane of said panel; comprising the steps of: moving said upper segment outwardly from the plane of said panel; inserting said extension along the inside of said panel; preparing the outer surface of said extension for adherence to the inner surface of said upper segment; and adhering the outer surface of said extension to the inner surface of said upper segment.

2. A method in accordance with claim 1 wherein said upper segment is moved outwardly from the plane of said panel subsequent to insertion of said extension 3. A method in accordance with claim 1 wherein said at least one extension is the front flap thereof.

4. A method in accordance with claim I wherein said at least one extension is the side flaps thereof.

5. A method in accordance with claim I wherein said extension and upper segment are of complementary configuration and said carton includes a thermoplastic surface coating whereby said adhering is accomplished by heat sealing the outer surface coating of said extension to the inner surface coating of said upper segment.

6. A method in accordance with claim 1 and further characterized by said adhering being accomplished through the use of a thermoplastic coating tha becomes tacky when subjected to sufficient heat.

7. A method in accordance with claim I wherein said extension and upper segment are of complementary trapezoidal configuration.

8. A method in accordance with claim 7 wherein the lengths of the parallel edges of said trapezoidal extension are in excess of the lengths of the corresponding edges of said trapezoidal upper segment.

9. A process for sealing a top-closing carton having an open topped body of a height defined by four interconnected sidewalls, a lid having a first edge thereof hingedly secured to the upper edge of one of said sidewalls and including a pair of flaps hingedly secured to second and third edges of said lid, the remaining edge of said lid having an extension thereon, comprising the steps of: forming a scoreline extending across at least a portion of the length of the sidewall to be aligned with said extension at a location intermediate its height to correspond to the width of said extension; moving said upper seg ment out of the plane of said sidewall; moving said lid into covering relationship with the top of said body; moving said extension into said body and adhering the outside of said extension to the inside of said segment. 

1. A method of closing a top-opening carton having a lid including at least one extension for contiguous association with a wall panel having an upper segment movable from the plane of said panel; comprising the steps of: moving said upper segment outwardly from the plane of said panel; inserting said extension along the inside of said panel; preparing the outer surface of said extension for adherence to the inner surface of said upper segment; and adhering the outer surface of said extension to the inner surface of said upper segment.
 2. A method in accordance with claim 1 wherein said upper segment is moved outwardly from the plane of said panel subsequent to insertion of said extension
 3. A method in accordance with claim 1 wherein said at least one extension is the front flap thereof.
 4. A method in accordance with claim 1 wherein said at least one extension is the side flaps thereof.
 5. A method in accordance with claim 1 wherein said extension and upper segment are of complementary configuration and said carton includes a thermoplastic surface coating whereby said adhering is accomplished by heat sealing the outer surface coating of said extension to the inner surface coating of said upper segment.
 6. A method in accordance with claim 1 and further characterized by said adhering being accomplished through the use of a thermoplastic coating that becomes tacky when subjected to sufficient heat.
 7. A method in accordance with claim 1 wherein said extension and upper segment are of complementary trapezoidal configuration.
 8. A method in accordance with claim 7 wherein the lengths of the parallel edges of said trapezoidal extension are in excess of the lengths of the corresponding edges of said trapezoidal upper segment.
 9. A process for sealing a top-closing carton having an open topped body of a height defined by four interconnected sidewalls, a lid having a first edge thereof hingedly secured to the upper edge of one of said sidewalls and including a pair of flaps hingedly secured to second and third edges of said lid, the remaining edge of said lid having an extension thereon, comprising the steps of: forming a scoreline extending across at least a portion of the length of the sidewall to be aligned with said extension at a location intermediate its height to correspond to the width of said extension; moving said upper segment out of the plane of said sidewall; moving said lid into covering relationship with the top of said body; moving said extension into said body and adhering the outside of said extension to the inside of said segment. 